Michael John Hayes has been sentenced to 12 months home detention after supplying guns to double murderer Quinn Patterson.

Hayes had pleaded guilty to three charges of unlawful possession of a military style semi-automatic, three charges of unlawfully supplying a military style semi-automatic to a person who does not hold a permit and three charges of supplying a firearm to an unlicensed person.

His family, including wife and daughter, sobbed in court as sentence was handed down.

The charges were laid after police discovered Michael Hayes left six of his firearms at Patterson's rental property on the outskirts of Whangarei before he killed two women.

The guns were left there after Hayes visited Patterson's house to do some target practice. Patterson was not a licenced gun owner, but had set up a makeshift shooting range at the property.

After leaving the guns at Patterson's place, Hayes never returned to collect the firearms. Patterson used Hayes' gun licence number and Hayes' name to bid on guns on the auction site Trade Me.

A total of four shotguns, four .22 calibre rifles and two 7.62 calibre AK-47 type weapons were purchased through Patterson's Trade Me account.

When interviewed by police, Hayes said the agreement was that Patterson would purchase the guns, but Hayes would have custody of them and Patterson would only take ownership when he got his gun licence.

Patterson had told Hayes that he wanted to get a gun licence and had asked Hayes if he would be a referee. Hayes agreed, but Patterson's application was rejected by police on the basis that he was not a fit and proper person.

It's understood Patterson did not inform Hayes that police had turned down his request.

On July 26, 2017, mother and daughter Wendy Campbell-Rodgers and Natanya Campbell went to Patterson's address to conduct a property inspection. They were accompanied by contractor Jeff Pipe and the plan was to install some smoke alarms.

Patterson shot and killed Ms Campbell and Ms Campbell-Rodgers. Mr Pipe was also shot, but he survived.

Police unsuccessfully tried to negotiate with Patterson and fired tear gas into the house. Patterson then fired several rounds at police with a large calibre semi-automatic.

While Patterson was still inside the house, an intense fire erupted destroying the dwelling. Patterson's body was later recovered from the scene.

The case summary of facts states that analysis of the cartridges fired by the murder weapon showed it was a .22 calibre weapon, with a "similar" firing pin to the Gervarm .22 calibre rifle.

Hayes had left two Gevarm .22 calibre rifles at Patterson's house when he'd visited to do target practice. A further 3 Gervarm E1 semi automatic .22 calibre rifles were purchased using Patterson's Trade Me account.

However, the summary of facts stops short of saying the murder weapon was in fact one of Hayes guns.

A total of 15 firearms were found by police - 11 recovered from Patterson's burnt-out rental home and four guns were found at Hayes' address.

Hayes' lawyer, Arthur Fairley, has previously stated that there's no evidence one of Hayes' guns was used to fire the fatal shots, and a Judge has ruled that the deaths of Ms Campbell and Ms Campbell-Rogers would not be an aggravating factor during sentencing.

"The Crown are not advancing as an aggravating factor that the death weapon is attributable to my client", Mr Fairley told Newshub in May.